For years, it has been recognized that the efficiency and power of an internal combustion engine, especially of the compression ignition type, could be substantially improved by boosting the intake manifold pressure. This is normally accomplished by means of a turbocharger including an impeller-type compressor powered by an exhaust driven turbine. When the internal combustion engine is used in conjunction with a compressed air utilizing device, such as an air compressor driven by the engine, it seems only logical to also use the compressor component of the turbocharger to provide a first stage boost for the engine driven air compressor thereby enabling significantly higher mass delivery and output air pressures for the same weight unit. One example of an exhaust driven turbocharger being used to provide intake manifold boost and first stage compression for an engine/compressor unit is illustrated in U.S. Pat. No. 3,204,850 to Crooks.
While turbocharged engine/compressor units of the type described above are excellent in concept, special problems arise when conventional turbochargers are selected to meet the peculiar demands of an engine/compressor unit. In particular, conventional turbocharger units are normally designed to receive exhaust gas from and supply air to the same engine cylinders. Thus, when the conventional turbocharger compressor is called upon to also supply air to an air compressor driven by the engine, the pressure boost and flow rate capacities of the compressor component of the turbocharger are normally inadequate. Simply selecting a larger conventional turbocharger does not solve the dilemma since the turbine component is then improperly sized for the available exhaust gases produced by the engine.
Despite the high costs involved, designers have considered specialized turbocharger units for use in engine/compressor units which employ a single multicylinder block and a single crankshaft for interconnecting both compressor pistons and engine pistons. Such units reduce the normally difficult problems associated with accommodating wide spacing between the engine and compressor cylinders. In an apparent attempt to capitalize on the inherent spacing advantage, U.S. Pat. No. 2,628,015 discloses a turbocharged single block engine/compressor in which the problem of improperly sizing the turbine and compressor components has been alleviated somewhat by directly coupling the turbocharger shaft to the crankshaft of the engine/compressor. While this approach may provide the additional drive to the turbocharger necessary to provide the desired quantity and pressure of compressed air, the added expense of providing a gear connection between the turbocharger and the engine/compressor unit reduces significantly the overall advantages associated with this design.
Numerous attempts have been made to achieve flexibility in turbocharger applications by arranging plural or compound turbocharger systems which may be altered in accordance with changes in the operating conditions of the engine unit to which the turbocharger system output is supplied. For example, the following patents disclose various compound turbocharger systems:
U.S. Pat. No. 3,250,068 PA0 U.S. Pat. No. 3,941,104 PA0 U.K. Patent Application No. 2,034,815A PA0 Swiss Pat. No. 160,008 PA0 German Pat. No. 850,965 PA0 Russian Pat. No. 661,127
However, none of these compound turbocharger systems in any way addresses the problem of designing an exhaust driven turbocharger system using plural conventional exhaust driven turbocharger units to match the available requirements of an internal combustion engine while generating ample quantities of additional quantities of compressed gas.